Summary

On 25 January 2019, the structure damming a pond filled with iron ore mining wastes (tailings) burst at Brumadinho, Brazil (1), causing a massive mudslide that killed at least 232 people. This tailings dam failure was only the most recent in a long list of catastrophic tailings dam accidents (see the first figure) (2, 3). Similar accidents also occur at electric power stations, where ponds are used to store coal combustion residuals such as fly and bottom ash. There are about 1000 operating ash ponds in the United States (4), and coal consumption patterns suggest that there may be more than 9000 worldwide. The catastrophic accident at the Kingston fossil power plant in Tennessee in 2008 (5) highlights the destructive potential of ash pond failures. Detailed analysis of tailings dam and ash pond failures shows that little-understood processes such as time-delayed triggering mechanisms are more likely to manifest when best engineering practices are disregarded.